Accuracy of anatomic 3‐dimensionally printed canine humeral models

Abstract

Objective: To evaluate the accuracy of various three-dimensional print (3DP) technologies using morphometric measurements.Study design: Experimental. Sample population: Cadaveric canine humeri and size-matched 3DP models.Methods: Fiduciary radiopaque markers were affixed to canine humeri of three different sizes (4, 13, 29 kg) at predetermined anatomical landmarks. 3DP models were created using one of three printers; desktop printers Form 3L and Ultimaker 5S, and industrial printer Objet Connex (n = 5/group/ printer). Marker based morphometric dimensions between cadavers and 3DP models were statistically compared using 2-factor repeated measures ANOVA followed by Tukey's post-hoc test (p < .05).Results: Bone size and printer type both significantly affected 3DP accuracy, with size having the larger effect (p < .0001 and p < .02, respectively). Regardless of printing technology, model size was smaller than native bone in most cases. At the humeral condylar level, the best accuracy was seen in the medium-sized humerus with the Ultimaker printer ([0.09 mm], p < .03).Accuracy was reduced in the proximal humerus in all groups. Conclusion: Desktop printers were overall more accurate than the industrial printer. Although significant differences were identified between models of different sizes, the submillimetric magnitude of these differences is unlikely to be clinically relevant.Clinical significance: While preoperative planning using 3DP models is becoming mainstream, accurate representation of the actual bone is critical. This study demonstrates that common desktop printers are suitable for this purpose.

Post-sterilization Dimensional Accuracy of Methacrylate Monomer Biocompatible Three-Dimensionally Printed Mock Surgical Guides

“…Additionally, the majority of resins trended toward size over-estimation of printed replicas, which is different from other desktop printers and non-biocompatible resins. 6 Other post-sterilization dimensional studies do not directly report on under or over-estimation of measurements, which would be useful information for guide and instrument design. Indeed, while the magnitude of such changes is not likely to be a clinically relevant finding, it could be an important consideration when selecting tolerances in patient-specific guides.…”

“…The use of patient-specific instrumentation in joint replacement surgery could also become more mainstream, given the combined accuracy results from the biocompatible resins reported here and condylar accuracy results from a previous study. 6 While not directly related to accuracy, printing times and resin volumes should be a consideration in pre-operative planning. Indeed, printing times will affect the rapidity with which guides can be created or surgical planning can be performed.…”

“…This is notably smaller than an earlier report where the largest recorded absolute variation was 1 mm using desktop printers. 6 This may be, in part, due to the difference in model profile between studies. In the current investigation, measurements were comprised of simple geometric shapes, whereas the previous report evaluated a humeral replica with complex geometry.…”

“…Five biocompatible resins (various compositions of methacrylate monomers) were selected. Guides were printed using a desktop machine (Form 3B, Formlabs, Somerville, Massachusetts, United States), which was chosen based on the reported accuracy of a similar printer 6 and the available selection of biocompatible materials. Resins included surgical guide (SG), biomed amber (BA), biomed clear (BC), biomed white (BW, newly released) and biomed black (BB, newly released).…”

“…Sample size ( n = 5 / material / sterilization method) was based on previous studies using 3D printed or machined models. 6 29 30 31 Data distribution was evaluated for normality using the Shapiro–Wilk test. Mean dimensional differences (absolute value) between the designed guide and pre-sterilization models were first compared using a paired student t -test ( n = 15 / material).…”